Johanson



Aug. 15, 1950 s. JOHANSON 2,519,251

SHUTTER DISSOLVE IN SLIDE PROJECTORS Filed Aug. 2, 1946 v 4 Sheets-Sheet 2 INVENTOR.

STEN JOHANSON ATTORNEY I g- 15, 1950 s. JOHANSON v 2,519,251

SHUTTER DISSOLVE IN SLIDE PROJECTORS Filed Aug. 2, 1946 4 Sheets-Sheet 3 INVENTOR.

Stan Johonson BY s ATTORNEY 5, 1950 s. JOHANSON 2,519,251

7 SHUTTER DISSOLVE IN SLIDE PROJECTORS Filed Aug. 2, 1946 4 Sheets-Sheet 4 INVEN TOR. Sten Johunson Z ATTORNEY iatented Aug. 15, 1950 2,519,251 SHUTTER DISSOLVE IN SLIDE PROJECTORS Sten J ohanson, New York, N. Y., assignor to Universal Camera Corporation, New York, N. Y., a corporation of New York Application August 2, 1946, Serial N 0. 687,910

12 Claims.

This invention relates to an improvement in the construction of slide projectors, and more specifically to a device to be embodied in a slide projector for the purpose of fading out the projected image or cutting off the light from the screen while slides are being shifted.

Ordinary projectors do not comprise any such device, so that whenever a slide .is being withdrawn from, or shifted into, the proper position for projecting, the motion of the slide is clearly visible on the screen. This fact tends to interrupt the continuity of the subject being presented, distracting the spectators, and decreasing the educational or the entertainment efficacy of the presentation.

According to my invention, 1 embody in a slide projector a number of iris leaves constituting together a diaphragm having an aperture variable from, amaximum to zero, and I associate said leaves and combine them with means operatively connected with movable portions of the slide proj ector, whereby they operate in suitable synchronism with said movable portions.

The general object of my invention is to provide means in a slide projector for fading out the projected image or cutting off the light from the screen while the slides are being shifted.

A mor particular object is to provide means in a slide projector for cutting off the light from the screen, which means enter into operation whenever a slide is shifted'outwardly of the projector away from its projecting position, and which means are automatically returned to their inoperative position, allowing full lighting of the screen, as soon as a new slide is moved into the projecting position.

Another object is to provide in a slide projector a diaphragm comprising a number of iris leaves swingable, in synchronism from a position of complete apertur to one of complete closure, and means operatively connecting said iris leaves to slide holding means, whereby the operation of said diaphragm is controlled by the motion of said slide holding means.

A further object is to provide in a slide projector slide holding means reciprocable between two extreme positions in each of which one slide is in position for projecting and another slide is accessible for changing, and diaphragm means operatively connected to said slide holding means in such a manner as to cut off the light from the screen when said slide holding means are displaced from either of said extreme positions and as to allow of the free passage of light to the screen when said slide holding means go into either of said extreme positions.

A still further object is to provide in a slide projector slide holding means and diaphragm means according to the preceding object, which diaphragm means operate to cut off the light from the screen when said slide holding means are about to be displaced from either of their extreme positions, before any actual displacement occurs.

A still further object is to provide means in a slide projector achieving all of the aforementioned objects, which means are simple, foolproof and can be embodied in a slide projector at a very reasonable cost.

Other related and ancillary objects of my invention will clearly appear as the description proceeds.

In the drawings,

Fig. 1 is a vertical section of a slide projector embodying my invention, taken along the longitudinal axis of the projector.

Fig. 2 is a vertical section of the projector of Fig. 1 taken on the line 2-2 looking in the direction of the arrows.

Fig. 3 is an enlargement of a detail of Fig. 1 and precisely of the slide holder and diaphragm assembly.

Fig. 4 is a vertical section taken on the line 44 of Fig. 3, looking in the direction of the arrows, showing all the elements in their neutral position, by which word neutral is meant the position assumed by the elements while a slide is being projected on the screen.

Fig. 5 is a vertical section similar to Fig. 4, but showing all the elements thereof in the position they assume while slides are being changed and the slide holder assembly moves to the left, as viewed from the front of the projector.

Fig. 6 is a vertical section similar to Figs. 4 and 5 but showing all the elements in the position they assume while slides are being changed and the slide holder assembly moves to the right, as viewed from the front of the projector.

Referring now in detail to the drawings, the slide projector comprises a suitable casing I which is pivoted at 2 to a pedestal 3. A tie 4 is attached to a projection 5 of the casing I, and terminates with a screw threaded portion 6, engaged by a nut I outside the pedestal. A spring 8, held between the pedestal 3 and a sleeve 9 mounted at the tie 4 internally of the pedestal, normally urges the tie as far to the front of the projector as the nut 1 will allow it to go, so that by screwing in the nut I, the tie can be pulled to the rear, and the projector casing I will slant with its forward end downwardly.

Inside the casing l are carried a source of asiacti light it, a reflector ll, condensing lenses i2, a slide holder and diaphragm assembly generally designated at is and a group of objective lenses i4, mounted in the objective slide l for focusing. The slide holder and diaphragm assembly 13 is the portion of the projector with which this invention is particularly concerned and is therefore illustrated at a greater scale and in various positions in Figs. 3, 4, 5 and 6.

The said slide holder and diaphragm assembly comprises a diaphragm to be described later and. a double slide holder iii-ll. Said slide holder, as best shown in Fig. 3, comprises elements i3, i9, 29 and 2| suitably interconnected, such as by spot welding, in a rigid manner. The whole slide holder and diaphragm assembly. is encased:

by plates 22 and 23, connected by means, of bolts, E i and 25, which together constitute a frame for the assembly. Plate 22, which is bent at right anglesin five places, asillustrated in Fig: 1, also has-aprojection 25, whichfits in a groove 2? formed internally of thecasing I to provide bottom support to the assembly. A slide bar 28' whichmay have the shape of an angle elemen-t, as illustrated in the drawings; is'inserted in acomplementarily shaped groove of the slide holder iti l, Said slide bar 23 is longerthan-the doubleslide hold'er, so that it protrudes with a portion-- such as that indicated at 2-9 in Fig. 2 at one on the other side of the double slide holder. The length of' said protruding portion 23, as will be pointed out hereinafter, isdetermined-by the operating requirements of the device; The slide bar ZE'is-bentat its-free end--by 90, such as shown at 31), so that it cannot slide with respect to the slide holder-by a. distance greater than the length of-the portion 25'; but must-inall motions-exceeding such lengthcarry the slide holder withit. The slidebar 23 is also grooved-or-notched in two places, at 3-! and 32, fol-the purpose which will hereafter be made apparent. A spring ii is attached'to theplate andpresses' downon the topof the slide holder, asbestshownin Fig; 2, toguideitinits sliding motion. Each section of the double-slide holder is adapted to receive a slide 33, and has a spring-3lto-hold the slide in-position. There are-two openings and 3t in-the slide holder.

In what follows, the diaphragm will be described at first-with'reference to the-positioned relationship of -its various component elements, which obtains when a slide is -being projected. Thediaphragm isthen in what will be called hereafter neutral position.

Mounted on bolt 25, there is a-sleeve 3?, round which is coiled a torsion spring 38. Freely mounted on the-sleeve 3-? to the rear thereof, there isa leverplate 39', whichlever-platetil is oonnectedtooneenddt of the torsion spring 38,- w-hiletheother end ll of thetorsio-n-spring 38. engages abore in-the-plate 23, which is stationary. Thus, the torsion spring 38- tends to maintain alever. plate-39 in its-neutral position, best. seen in Fig; 4. The lever plate 39 is recessed as shownat= i2 and this-.recessengages a pindsmounted-atthe bottomof alever ll, which will bedesignated as the motion transfer lever, for reasons that. will becomeapparent later.- Mounted on the leverplate 39, there pin 45,- Which penetrates inv one of the recesses 3| or 32 asthe case'may be, of theslide bar 28-. The motion transfer lever i l is pivoted 'to the'pi-vot post. it and carries at its upper end apin 41. Theleverplate 39'1has at its upper left hand portion, asviewedin Figs. Z-and 4, an-ear 48.

In addition to the pivot post 56, there are three other pivot posts, that is the spring post 39, and the two identical posts 59, which are countersunk as indicated at 5!, so that they will not interfere with the free motion of the slide holder. Each post comprises a bolt, and the bolt carries thereon; asleeve, such as: the sleeve 52', which is recessed such as at 53 to receive in peripheral engagement an iris rin 5 The four aforementioned posts, with their recessed sleeves, co- Qperateto; maintain the iris ring in position and guide it, while allowing it to rotate in situ about a. central point defined by the intersection of a line joinin the center of the post 45 to the center of the post 49 with a line joining the centers of the two-posts 53. It is to be noted that, this. central point is also a point of the optical axis of the projector. The iris ring 54 has a central opening 55 alined with the opening or 36, depending onwhich of the two happens to be in position for the projecting. The iris ring 5 3 also has therein four recesses 56. Onthe periphery of the iris ring 5:; there is a lug 5? adapted to-bear against the recess 53 of the sleeve 52 of the sprin post 49, and when it so bears, to prevent any clockwise rotation of the iris ring. The words clockwise and counterclockwise, as well as right and left, are to be construed,- wherever they occur, as referring to-a View of the device from the front of the-projector, as in the drawings. A tension spring 58*is-attached to the spring post it and tothe periphery ofthe-iris ring t i at 59, and normally urges the iris ring clockwise, thus causing thelug 57 to=bearon the post' lil, and maintaining, in cooperation with said lug and post, the iris ring in the neutral position of Fig. 4.

In addition to the elements alread described, the diaphragm comprises four iris leaves 6! pivoted oneeach to the post 56; the post 49 and the two posts 53'. One of said-leaves only is shown in Fig. 4, for thosake of simplicity, while all four areshown-inFigs. B and 6 in broken lines, as-they are located behind the plane 4-l along which-the sectionsof-Figs; 4, Band 6 aretaken.

The-leaf'pivoted to-the-post 46 is rigidly con-- netted through this pivot and also-through the pin 41- to the motion transfer lever fl. Each of the remaining iris leaves-has mounted thereon a pin 6.1-, analogous in position and function to thepintli Each ofs-aid pins-6i, and also the pin ll; engages one of= the recesses 53 of the iris ring- 54:; Each iris leaf has a recess it adapted to accommodateone of the posts lt-g 48' and-5t,

. when the leaf is in the neutral" position of Fig; 4.

Thoroughly to understand the operation of this device, let us-assume that itis initiall in the neutral=positi0n'ofFig. 4, which is-the same astheposition of Fig. 1, if it is-the section l! of theslide-holder that is alined with the iris ring andwith the opticalaxis of the projector. Then'said'section I? will housea slide, and'said slide is being or-can be projected; Gbviously, all the -elements of thediaphragmbeing in the position of Fig; 4, the-iris leaves are-swung outwardly, as clearly indicated in said figure, so that their inner-edges 62- substantially coincide with the inneredge S3 of the iris ring, in the portionv of said edge- 63- which are substantially circular; while-in the portions of said edge 63 which are substantially straight, the edges 52 are outwardly-of the edge 83. Thus the opening 55 0f the-irisri-ng. is completely free from obstructions, and light can pass therethrough to the screen.

, right.

thereof.

If nowit isdes iredlto change the slide, a new slide will be introduced into-the section l6 of the slide holder, which protrudes outwardly of the casing to the right of the projector, as viewed from the front in Fig. 1. Then the right-hand bent end 30 of the slide bar28 is manually urged to the left. At first, the slide bar slides with respect to the slide holder Iii-11 freely, without causing any motion of thislatten. No motion of any other parts occurs until the slide bar has moved by a distance equal to one-half the length of the portion 29 of the slide bar 28. At this pointthe right hand edge 54 of therecess 32 of the slide bar'engages the pin 45, and urges it to the left. This causes the lever plate 39 to swing counterclockwise, and as a result the pin 45 not only moves to the left, but also downwardly. Rotation of the lever plate 39 causes no motion of any other parts until the edge of the recess 42 engages the pin 43. Then the pin 43 is urged to the left, causing the motion transfer lever 3 to swing clockwise, carrying the pin 4? to the Concurrently, the torsion spring 33 is deformed against its elastic reaction.

,Rightward motion of the pin 41, because of the engagement of said pin with the recess 55 of the iris ring 54, causes said iris ring to rotate counterclockwise. Concurrently, rotation of the motion transfer lever 44 causes the iris leaf 6%? connected thereto to swing clockwise about its pivot post 46 and to assume the position shown in Fig. 5. Counterclockwise rotation of the iris ring 44 results in a stretching of the tension spring 58 beyond its normal tension, as the lug 5! becomes spaced to the left from the post d9. Concurrently, each pin 6| of an iris leaf all, through its engagement with a recess 55 of the iris ring is set in motion, the pin of the top leaf moving to the left, the pin of the left-hand leaf downwardly, and the pin of the right-hand leaf upwardly. As a result each iris leaf is forced to swing clockwise about its pivot fill or 55 as the case may be, in a manner analogous to the motion of the bottom iris leaf, already described. Thus all the iris leaves go to occupy the position shown in Fig. 5. i l

These motions are completed by the time the slide bar 28 has moved to the left by a space equal to the complete length of the portion 29 At this point the pin 45 has swung downwardly so far that its periphery at its uppermost point is no higher than the lower edge 5'5 of the slide bar, as shown in Fig. 5. Thereafter the slide bar rides over said pin 45, and the varie ous parts of the diaphragm assembly remain in the positionof Fig. 5, without further motion. Now, however, the bent end 39 of the slide bar contacts the end 6! of the section it of the slide holder. Then any further motion to the left of the slide bar causes an identical motion of the complete slide holder 5-41. As a result thereof, the section ll, carrying the slide which has already been projected, issues to the left from the casing I, while the section 15, carrying the: new slide goes into the projecting or neutral position. The slide bar now protrudes to the right of the slide holder 15-4! by an amount equal to the length of the portion 29. Before the motion of the slide holder has been completed, the edge 68 of the recess 3i of the slide bar reaches the uppermostpoint of the periphery of the pin 45. Thereafter the recess 3| overlies the pin 45, and said pin is no longer held in its left- Ward and downward position of Fig. 5. Then the elasticity of the. deformed torsion spring 36 comes into play; aiidswings' the lever plateIQQ clockwise back to its neutral position. The edge 55' of the recess 42 no longer operates to hold the pin 43 in the position of Fig. 5, and therefore the motion transfer lever 44, the iris rings 54, and the iris leaves 66 are free to return to the neutral position wherein they allow free passage of light to the screen, and they do so return, the motive power for their return motion being furnished by initially set forth.

the tension spring 58. Now the projector is once more ready for operation, all of its parts being in a position analogous to that of Fig. 1, except that now the section ll? of the slide holder is centered, while the section l'i protrudes outwardly of the casing I to the left, and the slider bar 28 protrudes to the left of the slide holder section ll by an amount equal to the length of the portion 29.

As soon as it is desired to change slides once more from this new position, after a new slide has been inserted into the section ll of the slide holder, the slide bar is pushed to the right. The same process already described now takes place once more, except that now the edge 68 of the recess 3i plays the part previously played by the edge 64 of the recess 32. The pin 45 is urged to the right, until it assumes the position of Fig. 6. The lever plate 39 swings clockwise to the position of Fig. 6. As soon as the edge of the lug 48 of the lever plate engages the pin 4'l, said pin 4? is urged to the right, causing the iris ring 54 and the iris leaves 55 exactly to repeat the motions described above. In due course, the slide bar 28 rides over the pin 45, and the diaphragm stays closed, while the slide holder continues to move to the right. Finally, the edge 64 of the recess 32 reaches the uppermost point of the periphery of the pin 45, accomplishing the function previously performed by the edge 68 of the recess 3i, and all the parts of the diaphragm return by spring action, as above described, to their neutral position of Fig. 4. Thus one complete cycle of operation has taken place which cycle can be repeated indefinitely. V

A preferred embodiment of this invention has been described, for the purpose of illustrating the same, and of showing how it achieves the objects It is clear, however, that a number of mechanical parts, as well as the particular shapes and arrangement thereof, can be varied, modified and adapted by a person skilled in the art, availing himself of a fair range of equivalent, without departing from the spirit of this invention or exceeding the scope of the claims. 5

I claim:

1. In a slide projector embodying a source of light, a slide holder embodying two sections for carrying: each a slide, said slide holder being reciprocable between two extreme positions in each of which one section of said slide holder is centrally alined with the optical axis of the projector so that the image of a slide carried therein can be projected on a screen while the other section of said slide holder is accessible for changing a slide carried therein, longitudinal slidable means mounted within and movable relative to and with said slide holder for periodically reciprocating said slide holder between said two extreme positions, and diaphragm means opera airmen 2.. a slide projector embodying a source; of light, a. slide holder embodying: two: sections: for carrying each: a slide,. said. slide holder being ro ciprocablebetween two=extreme positions; in each of. which one section of said slideholderis centrally alined with. the optical axis of? the projector so that-the image of a slidev carriedtherein can be projected one. screen while the-othensection of said slideholder is. accessible for chang'- ing a slide carried therein, diaphragm means for controlling the passage oi; light from said'source to the screen, and a. longitudinally slidable and reciprocable member mounted within and. mov able relative to and with said slideholderopera tively associatedwith said slide holder and said diaphragm means and actuatable uponzdisplacement first to close said diaphragm means and subsequently to move said slide holdenfrom one to the other of said: extreme positionsthereof, said. reciprocable: member thereafter acting: on said. diaphragm. means to reopen the samewhen said slide holder nears one of saidex-ti nme po sitions;

3. In aslide projector, a;slideholden'a source of light, a diaphragm: interposed between: said source of light and a screen, means embodying tension spring; elements for urgingsaiddiaphragm to an open position; a longitudinally slidable member reciprocablerwithin and-:movable relative to. and with, and; periodically actuating said slideholder fordisplacingthe-same-beyond the axis of said'light-,,.said.member havingia-llimited lost motion with respect to=said:slide.-holder prior toactuating. this. latter,.and.motion transfer means operatively connectedwithzsaidxmem be: and actuatedv by said member during. the movement providing said lost motion-thereof relative-to saidslide holder to closesaid' diaphragm;

4. In a slide. projectonaisource of. light, a slide holder, embodying two sections for carrying. each one slide,=,saidslide holderbeing-normally in one' of two extreme positions in each of. which one section of said: slideholder is centrally alined with the optical axis ofthe projector so that the imageor a slide carried: therein can..be projected ona screen whilethe. other'sectionbfsaid slide holder is accessible for. changing a slide.- carried therein, said slide 'holderl'being longitudinally. reciprocable between said. two. extreme positions,- a diaphragm. interposed between said: source of light and the screen, means-.embodying.tension springelements fornormally maintaining said diaphragm in anopen'position; a member slidable withinand: movable relative. to and; with, and periodically actuating said slide holder between said two extreme positions, said=member havinga limitedzlostmotionwith respect to said slide holder prior to-actuatingethe'same periodically actuatable, motion transfermeans operatively-connected to saidimember and said-diaphragm, means embodying; tension elements for normally maintaining said motiontransferimeanainameutral position, said motion transfer'means-when they depart from-said neutral position: causing said -diaphragm to close, said=mernber during;the

movement providing said .lost motion thereof ac:- tuating: said motion. transfer. means; to. depart from i said: neutral position .1 thereof and allowing the same. to. returnito said neutral. position when said slide holder nearsone of. .said1extreme:-posi+ tionsithereof.

5. In a slide projector; embodying: a-sonrce: of light, arslidehold'er' embodying twossections for carrying eacln aslide, said slide. holderrbeingire oiprocable between two extreme positionadneach or which one section or said slide holder is centrally alined with the optical axis of the projec tor so that the image of a slide carried therein can be projected on" a'screen while the otherseotioncf said slide. holder is accessible for chang i n'g' a; slide. carried therein, a number of iris leaves swingable-in synchronism between an open' and -a closed position tocontrol the passage of light to the sereen, and'a movable member mounted with-- in andlongitudina'lly reciprocable relative to and with said slide holder operatively' associated with said slide holder and said" iris leaves, said mov able member; when. actuated; operating firstto causesaid iris leaves to assume said closed posi-- tion thereof and subsequently; to move said slide holder from one tothe other of said extreme positions thereof, said movable member allowing said iris leaves to-return to said open position thereof, when said slide holder nears an extreme position.

6; In a slide projector, a slide holder, a-n-iimber of iris leaves swingable in synchronism between an open and a closedposition; a member operatively connected-to said iris leaves and'having a neutral position: wherein said iris leaves arc-open and a displaced position wherein said iris leaves are closed, tension spring means for urging said member to the neutral position thereof, and means mounted within and longitudinally reciprocable relative to and with said slide: holder for causing. said member toassume said displaced position and-for moving said slide holder to make it-possible to change slides.

'7. In a slide projector, a slide holder, a number of iris leaves swingable in'synchronism' between an open and closed position, a member operatively connected to said irisleaves, said member having a neutral position wherein said iris leaves are open and being rotatable toa displaced position wherein said-iris leaves are closed, tension spring. means for urging said member to the neutral position-thereof, lever means operatively connected to-said-member, said lever means having a neutral position corresponding to'the neutral position of said member andbeingswingable from said neutral position to overcome said tension spring. means andcause said member to assumethe displaced position thereof, tension spring" means'urging said lever means to their neutral position, and means mounted within and longitudinallyreciprocablerelative to and with said slide holder for swinging said lever means from their neutral position-and formoving said slide holder to make it possible t'o change slides.

8. In a slideprojectona slide holder, a number of iris leaves swingable: in synchronism between an'open and a closed position, a memberioperatively connectedto said irisleaves and having a neutral positionwherein said iris leaves'are open and a displaced position wherein saidiris leaves: are closed, tension springeme'ans for urging said member to the neutral po'sition'thereof, and. a reciprocable-member mounted within and longitudinally reciprocable relative to-and with said. slide'holder operatively: associated with said slide holder and said-member, said reciprocable member operating duriiigafirst'par't of its stroke to move said member to the displaced'position thereof, and during asubsequent part of its stroke'to movesaid slide holder to make it possible' to change slides: and to allow said tension spring means to return said member to-its nedtra l. position.

51. vIn a slide'projec'tor; a'slide holder; a number of iris leaves swingabie'in synchromsm between.

an open and closed position, a member operatively connected to said iris leaves, said member hav 'ing a neutral position wherein said iris leaves are open and being rotatable to a. displaced position wherein said iris leaves are closed, tension spring means for urging said member to the'neutral position thereof, lever means operatively connected to saidmember, said lever means having a neutral position corresponding to the neutral position of said member and being swing-able 1 from said neutral position to overcome said ten-- -sion spring means and cause said member to assume the displaced position thereof, tension spring means urging said lever means to their neutral position, and a reciprocable member mounted within and longitudinally reciprocable relative .to and with said slide holder operatively associated with said slide holder and said lever means, said reciprocable member operating during a first part of its stroke to swing said lever means from their neutral position, and during a subsequentpart of its stroke to move said slide holder to make it possible to change slides and to allow said second mentioned resilient means to return said lever means to their neutral position.

10. In a slide projector, a frame, a slide holder having two operative positions in each of which a slide is in position for projecting and another slide is accessible for changing; a diaphragm, means for normally holding said diaphragm open, a lever pivoted in said frame, a pin rigid with said lever, tensionable means for normally urging said lever to a neutral position means for closing said diaphragm whenever said lever is displaced by a predetermined amount from its neutral position, a slidable member mounted within and reciprocable relative to and with said slide holder actuable to undergo a limited free displacement with respect to said slide holder when this latter is in one operative position and actuable to undergo further displacement with respect to said frame together with said slide holder while this latter is shifted to its other operative position, two recesses in said slidable member, one of said recesses receiving said pin when said slide holder is in an operative position, whereby when said slidable member undergoes said free displacement a shoulder of said recess receiving said pin acts thereon to cause said lever to be displaced by predetermined amount corresponding to the closing of said diaphragm, said slidable member preventing the return of said pin and said lever to the neutral position thereof while said slidable member undergoes said further displacement until the other recess of said slidable member receives said pin and allows said resilient means to return said lever to its neutral position.

11. In a slide projector, in combination with a frame, a slide holder having two operative positions in each of which a slide is in positionfor projecting and another slide is accessible for changing, and a diaphragm; tension spring means for holding said diaphragm open when'said slide holder is in an operative position, and means for closing said diaphragm when said slide holder is to be shifted away from an operative position; said means embodying a reciprocable member mounted within and longitudinally movable with and relative to said slide holder, a first lever pivoted in said frame, tension spring means for normally holding said first lever in a neutral position, means for swinging said first lever from its neutral position when said reciprocable member is actuated, a second lever pivoted in said frame, means for swinging said second lever when first lever is swung from its neutral position, and means for operatively connecting said second lever to said diaphragm, whereby the swingin of said second lever causes said diaphragm to close.

12. In a slide projector, a frame, a slide holder embodying two sections for carrying each a slide, said slide holder being reciprocal-ole between a first and second extreme position in each of which oneseetion of said slide holder is centrally alined with the optical axis of the projector while the other section is accessible for changing a slide carried therein; a reciprocable member mounted within slidable by a limited distance relative to said slide holder and further slidable therewith with respect to said frame; a diaphragm embodying a number of iris leaves swingable in synchronism between an open and a closed position, a rotatable ring, pin and recess means operatively connecting said ring and iris leaves, tensionable means normally holding said ring in a neutral position, means for preventing rotation of said ring in one direction, a rotation of said ring in the permissible direction causing said iris leaves to assume their closed positions; a first lever pivoted in said frame and having a recess and a lug; tensionable means for urging said first lever to a neutral position; a, pin rigid with said lever and engaging a first and a second recess in said reciprocable member respectively when said slide holder is in its first and second extreme positions; a second lever having a pivot in said frame, a first pin engaged by said recess of said first lever when this latter is displaced in one direction from its neutral position, and a second pin engaged by said lug of said first lever when this latter is displaced in the other direction from its neutral position, said first and second pin being on opposite sides of said pivot, said second pin also engaging at all times a recess in said ring; whereby when said slide holder is in its first extreme position and said reciprocable member slides with respect thereto, said first lever is caused to swing until the pin thereof goes out of engagement with said first recess of said reciprocable member, said recess of said first lever engages said first pin of said second lever causing this latter to swing, said second pin of said second lever causes said ring to rotate in said permissible direction, said ring causes said iris leaves to assume their closed position, and all the aforementioned elements remain in the position they have thus assumed while said slide holder moves to its second extreme position until said second recess of said reciprocable memleer reaches a position wherein it is engaged by said pin of said first lever, said second mentioned tensionable means return said first lever to its neutral position, said first mentioned resilient means return said ring to its neutral position, and said iris leaves are caused thereby to return to their closed position; and whereby when said slide holder is in its second extreme position and said reciprocable member initially slides with respect thereto, said first lever is caused to swing until the pin thereof goes out of engagement with said second recess of said reciprocable member, said lug of said first lever engages said second pin of said second lever causing this latter to swing and said ring to rotate in said permissible direction, said ring causes said iris leaves to assume their closed position, and :all the aforementioned elements remain in the position they have thus asslili i l While said slide holder moves to its first extreme position until said first recess of said reciprocable member reaches a position wherein it is engaged by said pin of said first lever, said second mentioned. tensionable means return said first lever to its neutral position, said first mentioned tensionable means return said ring to its neutral position, and said iris leaves are caused thereby to return to their open position.

'STEN J CHAN-SON.

REFERENCES CITED Number Number 12 UNITED STATES PATENTS Name Date Shannon Mar. :24, 1891 Force Sept, 6, 1892 Hastings et a1 July 14, 1896 Oldfield et a1. Mar. 15, 1910 Partington Feb. 22, 1916 England Mar. 5, 1918 FOREIGN PATENTS Country Date Great Britain of 1891 

